This invention relates to a metal honeycomb body for supporting a catalyst for purifying an exhaust gas emitted from an internal combustion engine such as an automobile engine, and a method for producing the same.
A metal support having excellent initial purification performance of an exhaust gas and a small exhaust resistance has been used recently, in many cases, for a catalyst device of an automobile. The metal support of this kind uses a cylindrical honeycomb body produced by superposing a metal flat foil with a metal corrugated foil, that is obtained by subjecting the metal flat foil to plastic processing into a corrugation form, with one another, and winding them into a spiral shape, or a honeycomb body produced by superposing alternately plane-wise the flat foil and the corrugated foil. The metal honeycomb body is then assembled into a casing such as a metal outer cylinder and the two parts are mutually bonded. After a catalyst is fitted to and supported by the metal honeycomb body, the resulting catalyst device is used as an exhaust gas purification apparatus for the automobile.
As shown in FIG. 1, for example, a conventional metal support 1 is produced by assembling a metal honeycomb body 2 formed of heat-resistant stainless steel foils into an outer cylinder 3 made of a metal. The metal honeycomb body 2 is produced mainly by superposing an about 50 xcexcm-thick belt-like flat foil 5 with a belt-like corrugated foil 6, that is obtained by subjecting the flat foil 5 to corrugation shaping, and winding these foils into a spiral shape round a take-up axis S indicated by arrow B in a direction as shown in FIG. 2. A ridgeline 7 of each corrugation is formed on the belt-like corrugated foil 6 in a width-wise direction. The circular cylindrical metal honeycomb body 2 wound into the spiral shape has a large number of vent holes 4 in the axial direction of the circular cylinder. The catalyst is supported by these vent holes, forming a catalyst converter.
The catalyst support must have excellent durability in order to withstand severe heat cycles, due to a high temperature exhaust gas from an engine, and also to withstand vigorous vibration from the engine. Therefore, in the metal support 1 according to the prior art, the contact portions between the flat foil 5 and the corrugated foil 6 of the honeycomb body 2 are bonded, and the outer periphery of the metal honeycomb body 2 and the inner periphery of the outer cylinder 3 are bonded, too.
Generally, the metal foil that constitutes the metal honeycomb body mostly uses a high heat-resistant stainless steel formed of Crxe2x80x94Alxe2x80x94Fe. For, aluminum (Al) in the foil is selectively oxidized on the surface to form Al2O3, improving thereby the oxidation resistance. Therefore, the Al amount in the metal foil exerts significant influences on durability of the metal support.
Bonding inside the metal honeycomb body is executed by fixing a Ni type powdery brazing material to the contact portions between the flat metal foil and the corrugated metal foil through an organic material such as a binder, and conducting a brazing treatment inside a vacuum furnace. In this case, Al in the metal foils tends to combine extremely strongly and firmly with Ni in the brazing material, and Al segregates near the brazing portion. On the other hand, Al in the proximity of the segregation portion becomes lean. In consequence, the oxidation resistance is deteriorated locally and invites a problem in durability. Furthermore, the brazing material is extremely expensive from the aspect of the production cost, and impedes the supply of economical metal supports to users.
Therefore, several methods of producing the metal support without using the brazing material have been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No.1-266978 discloses a method of producing a metal honeycomb body by bonding a metal flat foil and a metal corrugated foil by a solid phase diffusion bonding method at a treating temperature of 1,200xc2x0 C. (850 to 1,200xc2x0 C. in claims) and a vacuum of 10xe2x88x926 Torr (10xe2x88x922 to 10xe2x88x926 Torr in claims). However, this method has failed to secure durability that is required for an exhaust gas. Since this reference does not describe the treating time and the Al amount after the treatment, the relationship of these factors to an exhaust gas purification performance is not clear, either. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 5-168947 proposes a method that conducts the treatment at a high temperature (1,400xc2x0 C.). However, since this method uses a jig for preventing Al evaporation, the method is not completely free from problems from the aspects of productivity and production cost.
Generally when diffusion bonding is executed, materials to be bonded are brought into close contact with each other, and a surface pressure is always applied to them during heating, too, by using a press device or a weight. However, it is not possible to apply, from the outside, such a surface pressure to the metal honeycomb body 2 wound spirally as described above. Therefore, the surface pressure is applied during winding by applying a back-tension to the flat foil 5 in a direction of arrow A as shown in FIG. 2, or by inserting the honeycomb body 2 into the outer cylinder 3 and then reducing the diameter of the outer cylinder 3.
However, back-tension during the-winding operation cannot apply a sufficient surface pressure to the outer peripheral portion of the metal honeycomb body 2, and contraction of the diameter of the outer cylinder 3 cannot provide a sufficient surface pressure, either. Even when they are used in combination, the surface pressure cannot be applied sufficiently to the intermediate portion between the center of the honeycomb body 2 and its outer peripheral portion. If the back-tension is raised in order to impart the surface pressure. necessary for the intermediate portion, the vent holes 4 at the center undergo buckling. If the contraction ratio is raised, on the other hand, the vent holes at the outer peripheral portion undergo buckling.
To solve this problem, the inventors of the present invention have found that diffusion bonding can be achieved satisfactorily from the center to the outer peripheral portion by reducing the surface coarseness of the flat foil 5 and the corrugated foil 6, and applying the back-tension and conducting contraction of the outer cylinder diameter to such a range in which the intermediate portion of the metal honeycomb body 2 does not undergo buckling. Consequently, the present invention sets the surface coarseness of the flat foil 5 and the corrugated foil 6 to 0.001 xcexcm to 0.2 xcexcm in terms of the mean coarseness (Ra). The present inventors have described this proposal in Japanese Unexamined Patent Publication (Kokai) No. 8-38912.
This prior art reference limits the surface coarseness of the flat foil 5 and the corrugated foil 6 to 0.001 to 0.2 xcexcm in terms of mean coarseness Ra, but does not mention the measuring direction of the surface coarseness. The reference also limits the contact width of the flat foil 5 and the corrugated foil 6 to at least 30 xcexcm in the length-wise direction. According to an Example of this reference, when the contact width of the flat foil and the corrugated foil is 20 xcexcm, contact defects occur even when Ra is 0.1 xcexcm.
According to observations by the present inventors, durability of the diffusion bond portion is not sufficient if the surface coarseness measured in the crossing direction (D direction) is great even though the surface coarseness measured in the longitudinal direction of the belt-like flat foil 5 and the corrugated foil 6 is within the range described above.
Japanese Unexamined Patent Publication (Kokai) No. 5-131144 proposes the construction in which each of the peak and the valley of each corrugation of the corrugated foil 6 defines a parallel portion having a width greater than the foil thickness, and after this corrugated foil 6 is superposed with the flat foil 5, both foils are wound spirally so as to bring them into planar contact, and thereafter the foils are diffusion-bonded to improve the bonding strength.
The technology of Japanese Unexamined Patent Publication (Kokai) No, 8-38912 described above reduces the surface coarseness of the flat foil 5 and the corrugated foil 6 and limits the contact width to at least 30 xcexcm. However, concrete examples of the contact width are 30 xcexcm and 200 xcexcm that are disclosed in Examples. Incidentally, this reference does not mention the measuring direction of the surface coarseness. According to the observation of the present inventors, even when the surface coarseness of the belt-like flat foil 5 and the corrugated foil 6 falls within the range described above, durability of diffusion bonding is not sufficient even at a contact width of 200 xcexcm, if the surface coarseness measured in the crossing direction (D direction) is great.
In the technology proposed in Japanese Unexamined Patent Publication (Kokai) No. 5-131144 mentioned above, the parallel portion is formed on each corrugation of the corrugated wave in order to bring the flat foil 5 and the corrugated foil 6 into surface contact. However, the reference stipulates only that the width of the parallel portion be at least the foil thickness, but does not describe the concrete size.
Furthermore, as to heating at the time of diffusion bonding, high temperature heating at 1,250xc2x0 C. or above has been employed in the past, but diffusion bonding at a lower temperature has also been desired.
Generally, when the catalyst support is used while being mounted and fixed to the exhaust gas system of the automobile engine, for example, the catalyst support receives vibration during the engine operation and is heated by the exhaust gas and by the catalytic reaction. It is rapidly heated at the start of the engine and at the time of acceleration, and is rapidly cooled at the time of braking and stopping. In this way, the heat cycle of rapid heatingxe2x80x94rapid cooling is repeated during driving, and the metal support expands and shrinks with such a heat cycle.
When the metal support is rapidly heated, the center portion of the metal honeycomb body, at which the flow velocity of the exhaust gas is the highest, is heated most rapidly. Therefore, the temperature difference is created with the outer cylinder exposed to the atmosphere and the outer peripheral portion of the metal honeycomb body keeping touch with the outer cylinder. Owing to this temperature difference, the stress resulting from the difference of heat expansion concentrates on the bond portion near the outer peripheral portion of the metal honeycomb body or on the bond portion between the metal honeycomb body and the outer cylinder, inviting breakage, buckling or peeling. When the metal support is rapidly cooled, a temperature difference occurs between the center portion of the metal honeycomb body, the temperature of which drops with the drop in temperature of the exhaust gas, and the outer peripheral portion of the metal honeycomb body, the temperature drop of which is retarded. The stress resulting from this difference of heat expansion concentrates at the portions near the outer peripheral portion of the metal honeycomb body and invites similarly breakage, buckling and peeling.
To cope with the problems described above, a method has been proposed which bonds only a part of the contact portions between the flat foil and the corrugated foil of the metal honeycomb body, or bonds them while leaving a part of the contact portion unbonded, in order to mitigate the stress concentration resulting from the difference of heat expansion and to improve durability. Japanese Unexamined Patent Publication (Kokai) No. 5-131144, for example, applies a bonding-preventing agent to a predetermined portion of the corrugated foil having parallel portions of a predetermined width greater than the foil thickness at the peak and valley of each corrugation, and winds the corrugated foil in superposition with the flat foil so that only desired portions of both foils can be diffusion-bonded strongly and firmly. Japanese Unexamined Patent Publication (Kokai) No. 7-328778 applies a diffusion-preventing agent to predetermined portions of the flat foil, and winds the flat foil in superposition with the corrugated foil so that only predetermined portions of both foils can be diffusion-bonded.
As another counter-measure, Japanese Unexamined Patent Publication (Kokai) No. 8-229411 describes a method of mitigating the stress concentration by partially bonding the metal honeycomb body and the outer cylinder. The bond portions between the metal honeycomb body and the outer cylinder are limited to the portions that have high diffusion-bonding strength in the axial direction of the metal honeycomb body, and the rest portions are left as the unbonded portion in order to prevent the occurrence, and growth, of cracks in the axial direction of the metal honeycomb body. A plurality, and a suitable number, of unbonded portions are disposed in the spaced-apart relation from the outermost periphery to the metal honeycomb body opposing the registration portions in order to prevent the growth of the cracks in the diametric direction of the metal honeycomb body.
Japanese Unexamined Patent Publication (Kokai) No. 5-131144 described above discloses concretely the metal supports having two kinds of structures. In the first structure, the several turns of the outer peripheral portion of the metal honeycomb body and the portion on the upper end face are diffusion-bonded with the center portion on the lower end face side being left unbonded. In the second structure, the several turns of the outer peripheral portion of the metal honeycomb body and the portions on both upper and lower end face sides are diffusion-bonded with the remaining center portion being left unbonded.
The inventors of the present invention have conducted cooling-heating durability tests by ordinary rapid heatingxe2x80x94rapid cooling cycles by actually mounting the metal supports having two kinds of structures described in Japanese Unexamined Patent Publication (Kokai) No. 5-131144 described above to the exhaust system of the gasoline engine. As a result, the present inventors have confirmed that the metal supports have excellent durability, but they are not entirely satisfactory in cooling-heating durability tests under a severe condition of between a high temperature of 950xc2x0 C. or above and 150xc2x0 C., for example.
The metal support described concretely in Japanese Unexamined Patent Publication (Kokai) No. 8-229411 does not have satisfactory durability, either, in the cooling-heating durability test under such a severe condition.
The technology described in Japanese Unexamined Patent Publication (Kokai) No. 7-328778 indicates that bonding at the unbonded portions can be prevented more reliably by applying the diffusion-preventing agent to the flat foil than to the corrugated foil. However, this reference does not describe concretely at which portions the unbonded portions are to be formed.
As another counter-measure for preventing breaking, buckling and peeling of the metal support due to expansion and shrinkage inside the honeycomb body resulting from the heat cycle of rapid heatingxe2x80x94rapid cooling described above, Japanese Unexamined Utility Model Publication (Kokai) No.3-61113 proposes a method which elongates the flat foil constituting the metal honeycomb body, winds it round the honeycomb body in such a manner as to form a multi-layered structure of the flat foil, and fuses the distal end portion of this flat foil to the outer cylinder. In this way, the device of this reference absorbs the expansion and shrinkage resulting from the heat cycle by the multi-layered structure of the flat foil, increases the bonding strength with the outer cylinder, and prevents the occurrence of clearance and cracks on or in the proximity of the outermost peripheral portion of the metal honeycomb body.
Another reference, i.e. Japanese Unexamined Utility Model Publication (Kokai) No. 5-9638, proposes a technology for improving outer shape accuracy of a metal support formed by laminating alternately flat sheets and corrugated sheets to form a layered member, and bending the layered member into an S shape, by elongating at least one of the corrugated sheet and the flat sheet constituting the layered member to a length greater than the length of the other of the corrugated sheet or flat sheet, and winding this extra-length portion round the outermost periphery.
A catalyst converter exhibits its function in the reaction for rendering detrimental gases in the exhaust gas nontoxic only when the temperature exceeds the activation temperature of the catalyst. Therefore, heating of the catalyst converter is preferably made as rapidly as possible. It is advantageous for accomplishing this object to introduce the high temperature exhaust gas by fitting the catalyst converter near the engine, and to heat it rapidly to a high temperature. However, the problem of the difference of heat expansion becomes more remarkable under this high temperature rapid heating.
According to the technologies described in Japanese Unexamined Utility Model Publication (Kokai) Nos. 3-61113 and 5-9638, the layers of the flat foil or the layers of the corrugated foil are not mutually bonded in the layered structure of the flat foil and the corrugated foil wound on the metal honeycomb body. Therefore, durability is not always satisfactory under the severe condition where the catalyst converter is fitted near the engine and is heated more rapidly to a higher temperature.
It is therefore an object of the present invention to provide a metal honeycomb body that is more advantageous than the prior art devices in all aspects of exhaust gas purification performance, engine durability and the production cost, by stipulating first the foil thickness, stipulating next the heat-treatment condition of solid phase diffusion bonding, and insuring sufficient mutual bonding of stainless steel foils, particularly, Al-containing high heat-resistant ferrite type stainless steel foils.
It is another object of the present invention to improve the surface condition of the metal foils in order to advantageously execute solid phase diffusion bonding of the metal foils of a metal honeycomb body.
It is another object of the present invention to improve the shape of the contact portions between the metal foils in order to reliably execute solid phase diffusion bonding between the metal foils of the honeycomb body.
It is still another object of the present invention to provide a metal support that enables the metal honeycomb body to withstand the severe condition of rapid heatingxe2x80x94rapid cooling heat cycles by the exhaust gas.
Hereinafter, means for accomplishing the objects described above will be explained.
The first feature of the present invention resides in a honeycomb body comprising a flat foil and a corrugated foil each formed of an Al-containing ferrite type stainless steel, wherein the thickness of at least one of the flat foil and the corrugated foil is limited to less than 40 xcexcm, preferably 10 to 35 xcexcm, and at least the portions of the foils that are subjected to mutual solid phase diffusion bonding contain at least 3.0 wt % of Al; and resides also in a method of producing a honeycomb body by heat-treating such a honeycomb body at a treatment temperature of 1,100 to 1,250xc2x0 C. for a treatment time of 30 to 90 minutes and to a vacuum of 3xc3x9710xe2x88x924 to 5xc3x9710xe2x88x925 Torr upon arrival at the treatment temperature, subjecting the contact portions between the flat foil and the corrugated foil of the honeycomb body to solid phase diffusion bonding, and producing the honeycomb body.
In other words, the foil thickness of the metal honeycomb body is limited to the foil thickness described above and the metal honeycomb body is heat-treated under the heat-treatment condition described above. In consequence, microscopic deformation occurs on the foil surface to such an extent as to fill unevenness on the surface of the foils, and macroscopic deformation is generated by deforming the top portions of the corrugated foil along the flat foil so as to drastically increase the contact area and to drastically improve solid diffusion bondability.
If the metal honeycomb body contains 3 to 10% of Al even after the heat-treatment described above, the amount of Al consumed during driving of the car (during the engine durability test), that is, about 3.0%, can be contained at the foil thickness of 10 xcexcm even when the heat-treatment described above is applied to the metal honeycomb body. In consequence, durability can be improved.
In the metal honeycomb body, the second feature of the present invention resides in a metal honeycomb body, wherein the surface coarseness or roughness of the flat foil and the corrugated foil formed of the Al-containing ferrite type stainless steel is 0.001 to 0.3 xcexcm in terms of the mean coarseness or roughness Rac in the direction of vent holes of the honeycomb body (in the width-wise direction of the foils), and/or the surface shape and condition or surface texture of the foils is at least 100 in terms of the number of peaks PPI per inch length in the direction of the vent holes, and the contact portions between the foils are bonded by diffusion bonding. Such diffusion bonding is preferably carried out at 1,100 to 1,250xc2x0 C. As used in the specification, the term surface coarseness is synonymous with the term surface roughness. As used in the specification, the term surface shape and condition is synonymous with the term surface texture.
Such a surface condition of the foils can improve the diffusion bonding ratio of the bond portions, and can suppress the evaporation of the heat-resistant alloy elements of both foils because the diffusion bonding temperature is as low as 1,250xc2x0 C. or below. The foil thickness is not limited, in particular. Particularly when the foil thickness is less than 40 xcexcm, however, the heat-treatment time can be shortened and the heat-treatment temperature can be lowered. Also, because the time for reaching the catalyst activation temperature (300 to 350xc2x0 C.) can be shortened, initial purification performance can be improved.
The honeycomb body described above is produced by the steps of corrugation-machining a belt-like flat foil having a surface coarseness of 0.001 to 0.3 xcexcm in terms of the mean coarseness in the width-wise direction and/or having a number of peaks PPI of at least 100 per inch length in the width-wise direction, so that the ridgeline of each corrugation extends in the width-wise direction, superposing the corrugated foil with the flat foil, winding them spirally into a honeycomb body, and heat-treating the honeycomb body at a temperature within the range of 1,100 to 1,250xc2x0 C. so as to bond the contact portions between these foils by diffusion bonding.
In the honeycomb body, the third feature of the present invention resides in the honeycomb body wherein the width of the contact portions between a belt-like flat foil and a corrugated foil, each formed of an Al-containing ferrite type stainless steel, in the longitudinal direction, is at least five times the thickness of each of the flat foil and the corrugated foil, and these foils are bonded by diffusion bonding. Preferably, back-tension of 0.2 to 1.5 kgf/cm per unit width of the flat foil, which is lower than in ordinary cases, is applied to the flat foil.
In the metal honeycomb body having such a construction, the contact width between the flat foil and the corrugated foil exceeds a specific width. Therefore, the metal vapor of Al, etc, fills the clearance of the contact portions between both foils, inhibits invasion of oxygen, and suppresses oxidation of Al2O3, etc, in the contact boundary. Consequently, the contact portions can be diffusion-bonded without particularly elevating the surface pressure.
The foil thickness in this case is not limited, in particular, in the same way as in the case of the xe2x80x9csecond featurexe2x80x9d.
The metal honeycomb body described above is produced by the steps of forming a parallel portion having a width at least five times the foil thickness at each of the top and valley of each corrugation of the belt-like corrugated foil, superposing the corrugated foil with the belt-like flat foil, and winding them spirally into the honeycomb body while applying back-tension of 0.2 to 1.5 kgf/cm per unit width of the flat foil, to the flat foil. This honeycomb body is heat-treated at a vacuum heat-treatment temperature of 1,100 to 1,250xc2x0 C. and preferably at a temperature T satisfying the following relation, in accordance with the mean coarseness Rac (xcexcm) of the flat foil in the width-wise direction:
104/(T+273)xe2x89xa6xe2x88x920.43 log Rac+6.43
Therefore, the diffusion bonding effect can be further obtained by using the foils having the surface coarseness described in the xe2x80x9csecond featurexe2x80x9d described above.
In the metal honeycomb body comprising foils formed of an Al-containing ferrite type stainless steel, the fourth feature of the present invention resides in the construction wherein a unbonded portion, at which the contact portion of the flat foil and the corrugated foil is not bonded, is formed at one or more positions that are spaced apart by at least xc2xd of the radius from the center axis of the metal honeycomb body and inside the outer periphery, in such a fashion as to extend from one of the ends on a gas exit side, as a start point, to a position falling within the range of length of {fraction (9/20)} to {fraction (9/10)} of the full length of the metal honeycomb body in the direction of the center axis, as an end point, to cover at least one turn round the full periphery, and the rest of contact portions between the flat foil and the corrugated foil are bonded by solid phase diffusion bonding.
Preferably, the bonded portion having a length not greater than xc2xd of the full length in the longitudinal direction of the metal honeycomb body is formed in the boundary between the metal honeycomb body and the outer cylinder with a position, that is spaced apart by at least ⅓ of the full length of the metal honeycomb body in the axial direction from one of the ends on a gas entry side being as the start point towards the other end on a gas exit side being an end point, and the rest of the portions of the boundary are unbonded portions.
When the unbonded portion is formed inside the metal honeycomb body under such a condition, the metal foil portions existing on the side of the center axis from the unbonded portion undergo shrinkage towards the gas exit side in accordance with the rapid heatingxe2x80x94rapid cooling cycle by the exhaust gas, mitigating the stress concentration. Consequently, the metal honeycomb body has excellent durability to such a heat cycle. The foil thickness in this case is not particularly limited in the same way as in the xe2x80x9csecond featurexe2x80x9d.
To produce the metal honeycomb body, the diffusion-preventing agent is applied to the unbonded portion, and after the belt-like metal foils are wound, the diffusion bonding treatment is carried out. In this case, after the belt-like metal foils are wound to form the metal honeycomb body, the honeycomb body is inserted into the outer cylinder. Then, after the brazing material is bonded to the bonding portion and the diffusion-preventing agent is applied to other positions, the diffusion bonding treatment can be carried out.
Therefore, the excellent metal support can be obtained by forming the unbonded portion in the metal honeycomb body described in each of the xe2x80x9cfirst to third featuresxe2x80x9d described above.
The fifth feature of the present invention is that a shell is formed by winding at least two turns a flat foil or a corrugated foil round the outer periphery of a metal honeycomb body comprising these flat and corrugated foils each being formed of an Al-containing ferrite type stainless steel, and the flat foils or the corrugated foils forming the shell are bonded to one another.
The metal honeycomb body formed in this way is inserted into the outer cylinder, and the foils are bonded mutually and the outer peripheral surface of the foils and the inner peripheral surface of the outer cylinder are bonded. In this way, the metal support is produced, and a catalyst is supported to form a catalyst converter. When this catalyst converter is used, a temperature difference occurs between the metal honeycomb body and the outer cylinder depending on the rapid heating and cooling cycles, and the stress resulting from the temperature difference concentrates on or near their boundary. However, the firm and integral shell can prevent breaking of the metal honeycomb body. Therefore, this metal support can improve durability against deviation in its axial direction.
The stress concentration occurring in the metal honeycomb body can be drastically mitigated by firmly protecting the periphery of the metal honeycomb body having therein the unbonded portions described in the xe2x80x9cfourth featurexe2x80x9d, by the shell described above and consequently, higher durability can be obtained against the deviation in the axial direction of the honeycomb body. The foil thickness in this case is not particularly limited in the same way as in the case of the xe2x80x9csecond featurexe2x80x9d.
The metal support described above is produced by the steps of winding further at least one turn a belt member of the flat foil or the corrugated foil, that forms the metal honeycomb body, round the outer periphery of the metal honeycomb body described above, assembling the resulting metal honeycomb body into the outer cylinder, conducting the bonding treatment, diffusion-bonding the metal foils constituting the metal honeycomb to one another and the metal foils constituting the shell to one another, and brazing the outer periphery of the shell and the outer cylinder by the brazing material.
Diffusion bonding described above is executed by vacuum heating treatment at a temperature within the range of 1,100 to 1,250xc2x0 C. However, the vacuum heat-treatment is preferably carried out at a temperature (Txc2x0C.) within the range given below in accordance with the foil thickness (t xcexcm) of the metal honeycomb body. The foil thickness of the metal honeycomb body is preferably less than 40 xcexcm. When the shell is formed by separately winding the foil belt, a foil having a thickness of 50 to 100 xcexcm may be used:
1,100xe2x89xa6Txe2x89xa61.7t+1,165